We report hardness and Young's modulus measurements on various dielectric thin films. Hardness and modulus information was derived from indentation experiments with a Berkovich triangular-based diamond indenter in an ultra micro-indentation instrument (UMIS). We studied the effect of moisture content and phosphorous doping on hardness and Young's modulus of low temperature Chemical Vapor Deposition (CVD) Si-oxides and found that dehydration and densification tend to harden samples, whereas increased P-doping results in a lower hardness. Hardness values of silicon nitride, silicon oxynitride, sputtered oxide, spin-on-glass and APCVD Si-oxides are compared. We also discuss how deposition conditions and chemical compositions correlate to dielectric properties such as stress as well as moisture uptake, thermal expansion coefficients and hardness and modulus values. Using these results, thermal stresses in encapsulated Al lines have been calculated and the calculated stress in Al is higher when encapsulated with dielectric films with higher moduli.